When sending text messages on your iPhone incomming messages are white, and outgoing are green.

In an effort to not over pursue a possible mate you make sure that you are in the white before sending a text. If the last two messages on your phone are green then you are offically "in the green" and should refrain from contact until your target gets back to you.

"Hey bro, did you text Ami about coming downtown?"

"No can do sir, I'm "in the green" and I don't want to over pursue. I have to wait until I'm "in the white"